Electric timepiece



D 1970 TADAYOSHI SHIMODAIRA 3,550,370

ELECTRIC TIMEPIECE Filed Dec. 5. 1967 5 Sheets-Sheet 1 P/Q/O/Q ART 2 2 29, 1970 TADAYOSHI SHIMODAIRA- ELECTRIC TIMEPIECE Filed Dec. 5, 1967 5 Sheets-Sheet 2 F/6.4B F/G.4C

Dec. 29, 1970 ELECTRIC TIMEPIECE 5 Sheets-Sheet 4 Filed Dec.

D 1970 I TADAYOSHI SHIMODAIRA 3,550,370

ELECTRIC TIMEPIECE Filed De. s. 1967 5 Sheets-Sheet 5 FIG.

United States Patent O 3,550,370 ELECTRIC TIMEPIECE Tadayoshi Shimodaira, Suwa-shi, Japan, assignor to Kabushiki Kaisha Suwa Seikosha Filed Dec. 5, 1967, Ser. No. 704,965

Claims priority, application Japan, Nov. 10, 1967,

Int. Cl. G04c 3/00 U.S. Cl. 58-23 3 Claims ABSTRACT OF THE DISCLOSURE A vibrator for an electric timepiece utilizing an oscillator as a time base including an inertia body formed from an arm having a mass disposed at each end thereof and a spring connected to said inertia body at a point intermediate said masses. The inertia body is symmetrically oscillated in a plane about an axis of symmetry, The inertia body is selected to have a center of gravity which moves in a straight line on said plane normal to said axis of symmetry.

SIMPLE DESCRIPTION OF FIGURES FIG. 1 is a plane view of a well known U-shaped vibrator, FIG. 2 and FIG. 3 are diagrams for describing the principle of this invention, FIGS. 4A, 4B and 4C are diagrams for describing the effect of this invention, FIGS. 5A and 5B represent a cross section view and a plane view of an experimental vibrator for substantiating the principle of this invention, FIGS. 6A and 6B represent the results measured on the vibrator of this invention, FIGS. 7A and 7B are a plane view and a cross section view of an embodiment of the vibrator used as time base in the electric time piece according to the invention, FIG. 8 a plane view of an embodiment of the electric timepiece according to the present invention, FIG. 9 shows an embodiment of the electric circuit in FIG. 8, FIG. 10 another embodiment of the standard oscillator used in the electric timepiece according to the invention, FIG. 11 electric circuit of the oscillator in FIG. 10.

DETAILED DESCRIPTION OF INVENTION The present invention relates to an electric timepiece and more particularly to an electric timepiece utilizing standard oscillator of relatively low frequency, that is several tens or hundreds of cycle, without position error.

As already known so far as reliability is concerned, a tuning fork of high Q value is much better than a balance wheel of low Q value, While the balance wheel of low frequency could render position error zero, which is impossible in the tuning fork watch. Besides in the tuning fork watch the construction or manufacturing of the device for converting the oscillation to rotation becomes difiicult because of its high frequency.

The object of the present invention is to provide a stabilized electric timepiece completely free from position error by utilizing an oscillator member with rotary inertia body without axis sustained on a base plate which possess rather high Q value.

Another object of the present invetnion is to facilitate manufacturing of the converting device by lowering frequency of the standard oscillator.

In a conventional U-shaped vibrator in FIG. 1 it is well known that the rotary center of the mass 1 lies around one third of the overall length of the spring 2 and that frequency of the vibrator varies according to its position in the gravity field.

FIG. 2 is a diagram representing an oscillating mode for describing the principle of the vibrator of this invention. In FIG. 2 masses 4 and 5 with quantity of mass m1 and m2 joined by arm 3 constitute rotary inertia body with its center of gravity at G. 2 is a plate spring with l in length, fixed on the plate 6 at point a by one end, connected to the arm 3 of said rotary inertia body at point b in such a way that the rotary center of the rotary inertia body is situated on the oscillating symmetrical axis M. This inertia body is oscillated mainly by rotary moment. In the vibrator of FIG. 2 position error in the gravity field can be eliminated by two methods like the following:

(1) By coinciding the center of gravity of the rotary inertia body with the rotary center,

(2) By displacing the center of gravity with rectilineal motion normal to symmetrical axis Y.

When the center of gravity coincides With the rotary center according to the method (1) the gravity has no effect on restoring force of the vibrator, accordingly position error can be eliminated. However, it is impossible to follow the method (1) as there is no fixed rotary center in the vibrator of this type. The reason for the above will be explained in the following with FIG. 3. In this case only spring 2 is suffered momental force, then the spring 2 deforms in circular arc, R being radius curvature of it. Y axis in FIG. 3 runs in parallel with the spring and x axis runs rectangular to y axis. When the displacement of G at the distance [1 from the poining point b in the direaction of x axis and y axis are Ax and Ay respectively, we obtain:

Omitting terms over four power of 0 in the Equations 4 and 5 and substituting the Equations 3, 4 and 5 in the Equations 1 and 2:

As 0 l, error caused by omission above mentioned is extremely small. As shown in the Equations 6 and 7 there exists no point Where both Ax and Ay become zero simultaneously.

In FIGS. 4A, 4B and 4C it is supposed that the length of the spring is infinite and that of the locus of motion of the center of gravity G are rectilinear, FIGS. 4A and 4B show a case where oscillating symmetrical axis Y lies in the gravity direction (shown by the arrow g). In this case moment by gravity is not produced if the center G of gravity of mass displaces with rectilinear motion due to its infinite length of rotary radius, accordingly frequency does not vary.

FIG. 4C shows a case when vibratory axis is inclined from the direction of gravity by at. Frequency effects by momental'force of gravity are of equal quantity on the right side and on the left side as shown in FIG.

4C, so they canceled each other and have no effect on frequency. Locus of motion of the center of gravity is given by the Equation 8 through the Equations 6 and 7:

Thus the Equation 9 represents the condition for eliminating position error.

In actual case both moment and bending force effect on the spring 2, then the Equation 9 is not satisfied entirely, the distance it between the joining point b and the center of gravity G is approximated to one third of the length l of the spring 2. Practical experience shows h lies between l/ 3 and l/ 2.

The following measurement should be done to prove the above matters. In FIGS. A and 5B, 7 is a pin for connecting the rotary inertia body consisted of the masses 4 and 5 and the arm 3 with the spring 2, and 8 is a pin for connecting the spring 2 on the plate 6. Position error varies sinusoidal when the vibrator shown in FIG. 5 changes its position. In FIG. 6A several sinusoidal curves are shown with different parameter 11. From the relation between maximum 1 and 11 shown in FIG. 6A We can obtain the condition for making 1 :0. In this case maximum 1; appears in two positions up and down, supposing up position with the mass 4 above the mass 5 and down position with the mass 4 under the mass 5. FIG. 6B is a graph representing the relation between 12 and the rate where h is the distance between the center of gravity G of the rotary inertia body and the point I) of the spring 2, A is frequency error in two positions up and down and f is natural frequency. Values in FIGS. 6A and 6B are obtained by measuring the oscillator shown in FIGS. 5A and 5B which has the length of the spring of 47.5 mm. and the frequency of 16.7 cycles/second. The graph of FIG. 6B shows that position error can be eliminated only when h=l6 mm. is attained. Naturally slope and the point where position error attains Zero vary according to the quantity of mass, length of the arm and the length of the spring. When rotating the inertia body with the center line K of the spring 2 as horizontal rotary axis it is necessary for the center of gravity G to be on the center line K of the spring 2 to make position error zero. The above measuring result shows that position error can be eliminated when the center of gravity G of the rotary inertia body situates on the rotary symmetrical axis M, preferably on the center line K of the spring 2, and lies around one third of the effective length l of the spring from one end b of the spring 2. FIGS. 7A and 7B represent an embodiment of the standard oscillator of the electric timepiece according to the present invention wherein the oscillator for eliminating moment produced at point a in FIG. 2 consists of a left hand oscillator 1 in which the rotary inertia body with the masses 4 and 5 and the arm 3 is connected to the spring 2 at point 12 and a right hand oscillator 1 in which the rotary inertia body with the masses 4 and 5' and the arm 3 is joined with the spring 2' at point b, the said oscillators being fixed on the plate 6 in symmetry with z axis and oscillating in the same oscillating plane.

FlGS. 8 and 9 represent a plane view and a circuit diagram of an embodiment of the electric timepiece according to the present invention wherein the oscillator in FIGS. 7A and 7B is used as time base. This oscillator comprises U-shaped spring 2, the left hand rotary inertia body composed of quantity of mass 5, the arm 3 and the magnetic cup 4 having hollow cylindrical yoke and permanent magnet in its center, in the opening of which is interposed coil 9 without touching each other, and the right hand rotary inertia body composed of quantity of mass 5, magnetic cup 4' and the arm 3' constructed in the same manner as the former rotary inertia body, both rotary inertia bodies being joined by the spring 2 and 2 fixed on the plate 6 at point a, and the ends of the springs being fixed on the arm 3 and 3' of the rotary inertia bodies by the pin 7 and 7 as was described in FIG. 7.

Oscillation of the oscillator above mentioned is transformed to the rotational movement of the ratchet wheel 10 by means of the spring 13 having click 11, engaging with the ratchet wheel 10 and fixed on the arm 3' by the pin 12. The spring 16 with click 14 engaging with the ratchet wheel 10 and fixed on the watch plate 6 by a pin 15 by one end prevents the reversal of the ratchet wheel 10 by the Well known method. The rotation of the said ratchet wheel 10 is transmitted to the second hand wheel 18 through pinion 17 in one body with the ratchet wheel 10 to indicate time by the second hand 19 on the second hand axis. Description of the trains from the second hand wheel 18 to the hour hand wheel is omitted here as it consists of the well known method. Said ratchet wheel 10 is driven one pitch with every oscillation of said oscillator by means of the click 11. Suppose that frequency of the oscillator is 60 cycles/sec, the numbers of the dent of the ratchet wheel is 300 and the pitch is 50 micron, we obtain 5 m./m. of the outer diameter of the ratchet wheel and 12 times of rotation per minute. Reduction rate from the ratchet Wheel to the second hand wheel being l/l2, the second hand wheel can be in direct engagement with the pinion of the ratchet wheel.

In the embodiment shown in FIG. 8 the battery is arranged on the left hand side of said oscillator, the electric circuit 21 on the right hand and one pole of the battery is earthed on the watch plate 6 through armature 22 and fixed screw 23.

In the electric circuit of an embodiment in FIG. 9 signal emitted by the oscillation detective coil 9 interposed in the magnetic cup 4 of the standard oscillator shown in FIG. 8 passes through bias circuit composed of condenser 24 and resistor 25, is amplified by transistor 26 and is given to the driving coil 9, the battery 20 being the power source.

Although the standard oscillator in the embodiment of the electric timepiece of the present invention in FIG. 8 is driven electromagnetically by the magnetic cup another method of maintaining the oscillation may be used.

FIG. 10 shows a method in which the oscillator is driven by piezo-electric element. The oscillator in FIG. 10 comprises a piezo-electric element 27 for detecting deformation of the spring 2, a piezo-electric element 27 which bends the spring 2 by detective signal amplified at the amplifier circuit 28, a left hand rotary inertia body having quantity of mass 4 and 5 and the arm 3, a right hand rotary inertia body having quantity of mass 4 and 5 and the arm 3' and the spring 2 and 2' fixed on the watch plate 6 at point a, the end of which being fixed on the right and left arm by thet pin 7 and 7 FIG. 11 represents connection of the electric circuit 28 in FIG. 10, signal emitted by the detective piezo-electric element 27 is given to the driving piezoelectric element 27 through the amplifier circuit of the transistor 29 and the transformer 30 for impedance matching. Resistor 31 is for bias and power source 32 is the source of energy.

The position to which the piezo-electric elements 27 and 27 are placed is not limited to the example shown in FIG. 10; it may be anywhere, provided that the spring shows enough deformation there. It is a matter of course that the detective element and the driving element of the electric circuit in FIG. 11 may be piezo-electric element or electro-magnetic element. The spring of the oscillator used in the standard of the electric timepiece according to the present invention is not limited to the plate spring, it may be any form of spring e.g. beam of uniform strength.

As described hereinbefore the electric timepiece according to the present invention is able to provide a watch with low frequency and without position error.

I claim:

1. In an electric timepiece utilizing an oscillator as a time base, the improvement which comprises a vibrator mounted within said electric timepiece and coupled to said oscillator comprising an inertia body formed from a pair of masses and a coupling member supporting said masses in spaced relation; and a spring means connected to said inertia body at a single contact point intermediate said masses, said spring being adapted to oscillate in a plane in a symmetrical mode about an axis, said inertia body being disposed substantially parallel with said symmetrical axis, said inertia body having a center of gravity disposed a distance from said contact point substantially equal to between one-third or more of the effective length of said spring means and less than one-half of said effective length, said inertia body center of gravity lying on an axis extending normally from said plane of oscillation and passing through a point on said spring means substantially spaced said distance along said spring means effective length from said contact point.

2. An electric timepiece as recited in claim 1, wherein said coupling member is bar-shaped.

3. In an electric timepiece utilizing an oscillator as a time base, the improvement which comprises a tuningfork type vibrator mounted Within said timepiece and coupled to said oscillator comprising two inertia bodies, each of said inertia bodies being formed from a pair of masses and arm having said masses mounted thereon in spaced relation; and a U-shaped spring member having a pair of tines, each connected to one of said inertia bodies at a single contact point on its respective arm intermediate its respective masses, each time of said spring being adapted to oscillate in a plane in a symmetrical mode about an axis, each inertia body being disposed substantially parallel with the symmetrical axis of its associated tine, each of said inertia bodies having a center of gravity disposed on a plane extending normally to its respective plane of oscillation, each of said normally extending planes passing through a point on its associated tine spaced a distance from the contact point between said tine and inertia body corresponding to between onethird or more of the efiective length of said tine and less than one-half of said tine.

References Cited FOREIGN PATENTS 1,480,848 5/1967 France 5823 RICHARD, B. WILKINSON, Primary Examiner E. C. SIMMONS, Assistant Examiner U.S. Cl. X.R. 310-37 

